1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a semiconductor device in which an anti-reflection film is employed.
2. Description of the Background Art
Conventionally, in a manufacturing process of a semiconductor device, an interconnection layer is formed on a substrate, and on that interconnection layer a resist film is formed. Using a predetermined light source for exposure, an exposure of a predetermined pattern is then effected on the resist film. Thereafter, development is performed to form the resist film having the predetermined pattern. Furthermore, the step of etching the interconnection layer on the substrate is employed, using this resist film as a mask.
However, when the exposure of the predetermined pattern is effected on the resist film, the shape of the pattern formed by the exposure of the resist film would be deformed from a desired shape if there is a difference in level at the underlying interconnection layer or the like, since the exposure light is reflected at the sloped portion caused by this difference in level at the interconnection layer underneath the resist film and is scattered within the resist film.
Referring first to FIG. 17, an interconnection layer 101 is formed on a substrate 100. On this interconnection layer 101, a resist film 102 is formed. When an exposure light 104 is directed to this resist film 102, a portion of the resist film 102 which is not intended to be exposed is subjected to exposure at a sloped portion (a region denoted in the figure by the circle Y) caused by the difference in level provided at the interconnection layer 101.
Referring to FIG. 18, if development is then effected on this resist film 102, the resist film is not formed to have a desired shape, meaning that the interconnection layer 101 cannot be etched to obtain a predetermined shape using this resist film. One way to solve this problem is to form an anti-reflection film underneath the resist film for preventing the scattering of the exposure light at the sloped portion caused by the difference in level at the interconnection layer.
Referring to FIG. 19, an interconnection layer 101 is formed on a substrate 100. On this interconnection layer 101 is formed an anti-reflection film 106 of an organic material which absorbs exposure light 104. A resist film 102 is formed on this anti-reflection film 106.
With this anti-reflection film 106 formed, exposure light 104 does not scatter as seen in FIG. 19 even when exposure light 104 is incident on the region of sloped portion Y caused by the difference in level, and thus it is possible to expose resist film 102 in a predetermined pattern. Thereafter, referring to FIG. 20, resist film 102 is subjected to development so that resist film 102 having a predetermined pattern can be obtained.
However, even in the above-described method in which anti-reflection film 106 is formed, when etching of resist film 102 is performed, anti-reflection film 106 is also etched away as shown in FIG. 20 which causes the formation of an undercut portion X, since resist film 102 and anti-reflection film 106 are both formed from organic type material. The formation of this undercut portion leads to peeling of the resist film as the pattern of the semiconductor device becomes smaller.
Also, there is a method of using an amorphous silicon consisting of an inorganic type material instead of this anti-reflection film 106 made of organic type material. However, although this anti-reflection film of amorphous silicon can reduce the scattering of the exposure light when a g-line having an exposure wavelength of 436 nm is employed, it cannot reduce the scattering of the exposure light sufficiently when i-line having a wavelength of 365 nm or a krF excimer laser light having a wavelength of 248 nm is used as the exposure light.
Thus, a method of manufacturing a semiconductor device employing a compound of metal-silicon-nitride as this anti-reflection film is disclosed in Japanese Patent Laying-Open No. 4-233719. FIGS. 21 to 24 are cross sectional views showing the steps of manufacturing the semiconductor device when a film consisting of the compound of metal-silicon-nitride is employed as the above-described anti-reflection film.
Referring first to FIG. 21, a dielectric layer 105 of silicon oxynitride is formed on a semiconductor substrate 100. A metal layer 101 of aluminum is formed on this dielectric layer 105 to provide a conductor pattern. On this metal layer 101, an anti-reflection film 106 including a compound of metal-silicon-nitride is formed. Metals such as titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, or tungsten may be used for the metal included in this anti-reflection film 106. A resist film 102 is formed on this anti-reflection film 106. Furthermore, a photomask 110 of a predetermined pattern is disposed above this resist film 102. Thereafter, by using this photomask 110, resist film 102 is irradiated with exposure light 104, thus a predetermined pattern is obtained.
Referring next to FIG. 22, resist film 102 is developed to form an opening 120 having a predetermined pattern. Then, referring to FIG. 23, anti-reflection film 106 and metal layer 101 are etched, using resist film 102 as a mask. Referring to FIG. 24, resist film 102 is then removed by a predetermined process thereby enabling the formation of metal layer 101 having a pattern of predetermined shape.
However, in the above-described prior art, metal layer 101 is formed of aluminum and the metal used for the anti-reflection film consisting of metal-silicon-nitride film may be titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, or the like. Accordingly, although the metal layer and the anti-reflection film can be formed by the use of the same apparatus, the target had to be altered.
Accordingly, the number of the steps for manufacturing the semiconductor device is increased which hampers the improvement in the productivity of the semiconductor device and hampers cost reduction. In addition, the wavelength of the exposure light will become shorter when the semiconductor device comes to be integrated to a higher degree, thus further requiring an anti-reflection film which can prevent the scattering of the exposure light.